A tray sealer is known from DE 102008030510 A1 comprising at least two feeding belts to form and position a group of trays for a gripper system at a respective distance relative to each other so that the trays can be transferred by a gripper system into the sealing station. The trays filled with a product are commonly provided to the feeding belts by an intermittently operating chain feeder and are received in a start/stop operation from the first feeding belt following upstream, the so-called collection belt, of the tray sealer. Alternatively, the trays can be halted upstream of the first feeding belt using a stopper and be provided as buffered trays closely spaced. An intermittently operating chain feeder in which the trays are manually filled with products along the transport path is disadvantageous and not ergonomic for the operating staff. A continuously moving chain feeder is much better for manual loading.
One embodiment of a continuously operated tray feeder is described in the still unpublished EP 12006757 of the applicant. Here the trays are provided on a continuously moving chain feeder with predetermined spacing to the two feeding belts for being received and grouped as well as posited for the gripper system of tray sealer. The trays transported on the chain feeder are, for example, automatically filled by fillers moving along with the chain feeder. To enable improved grouping for the feeding belts while at the same time continuously providing trays, a gap, which is respectively advantageous for the intermittently operating gripper system, is already provided on the chain feeder between the groups of trays so that the feeding belts can, independently of the provision of trays by the chain feeder at least for a specific period of time, transport the group of trays to a position at which the gripper system takes them from the second feeding belt and feeds them to a sealing station of the tray sealer. Since only a complete group may be processed in the sealing station or have a top film be sealed onto the tray edge, respectively, it must be ensured that the defined arrangement of trays and gaps is maintained on the chain guide. Errors can be detected by inspection using sensors for the presence of trays, but in the event of an error, a correction must be made and the operation of the chain feeder must be halted. Errors caused by the operating staff, for example, due to a missing tray or a tray incorrectly inserted into the gap lead to a halt in the operation of the tray sealer and consequently of the chain feeder, which results in downtime and lesser productivity.